System and method for high frequency accoustic dampers with caps

ABSTRACT

An acoustic damper for a rotary machine includes at least one wall, at least one cooling air inlet, at least one outlet, and at least one cap. The at least one wall extends from a back side of a burner front panel such that the at least one wall partially defines a dampening chamber. The at least one cooling air inlet is defined within the back side of the front panel and is configured to channel a flow of cooling air into the dampening chamber. The at least one outlet is defined within the back side of the front panel and is configured to channel the flow of cooling air out of the dampening chamber. The at least one cap is positioned at least partially over the at least one cooling air inlet and is configured to reduce a velocity of the flow of cooling air within the dampening chamber.

BACKGROUND

The field of the disclosure relates generally to gas turbine engines, and more particularly to a high frequency dampers used within gas turbine engines.

Gas turbine engines typically include at least one compressor, at least one burner, and at least one turbine arranged in a serial flow configuration. Typically, the compressor channels compressed air to the burner where it is mixed with a flow of fuel and combusted, creating a high temperature flow of combustion gas that is channeled to the turbine. However, combustion within at least some burners may be unstable because the combustion dynamics within the burner may be unstable. Specifically, heat released during combustion, combined with the increased pressure caused by combustion, may cause acoustic pressure oscillations to develop within the burner.

Within known burners, the acoustic pressure oscillations typically occur during normal operating conditions and may depend on a fuel-to-air stoichiometry within the burner, a total mass flow within the burner, and/or other operating conditions. Over time, the acoustic pressure oscillations may cause equipment damage or other operational problems. To facilitate reducing the effect of the acoustic pressure oscillations, at least some burners include at least one acoustic damper that absorbs the acoustic pressure oscillations and that reduces the amplitude of the pressure oscillations. To prevent damage to the acoustic damper and to keep the acoustic damper clean, a flow of compressed cooling air is channeled into the acoustic damper. However, if the flow of compressed cooling air enters the acoustic damper at a high velocity, the pressure within the acoustic damper may decrease, allowing hot combustion gases to flow into the acoustic damper. In contrast, if the flow of cooling air is at a low velocity, cooling may be ineffective within the acoustic damper.

BRIEF DESCRIPTION

In one aspect, an acoustic damper for a rotary machine is provided. The rotary machine includes at least one burner including a front panel having a front side and an opposing back side. The acoustic damper includes at least one wall, at least one cooling air inlet, at least one outlet, and at least one cap. The at least one wall extends from the back side of the front panel and defines a dampening chamber. The at least one cooling air inlet is defined within the back side of the front panel and is configured to channel a flow of cooling air into the dampening chamber. The at least one outlet is defined within the back side of the front panel and is configured to channel the flow of cooling air out of the dampening chamber. The at least one cap is positioned at least partially over the at least one cooling air inlet and is configured to reduce a velocity of the flow of cooling air within the dampening chamber.

In another aspect, a method of manufacturing an acoustic damper on a front panel of a burner is provided. The method includes defining an outlet through the front panel. The outlet extends from a front side of the front panel to a back side of the front panel. The method also includes defining at least one cooling air inlet within the back side of the front panel. The method further includes forming at least one wall on the back side of the front panel. The at least one wall and the back side of the front panel defining a dampening chamber. The method also includes forming at least one cap positioned at least partially over the at least one cooling air inlet. The at least one cap is configured to reduce a velocity of a flow of cooling air within the dampening chamber.

In another aspect, a rotary machine is provided. The rotary machine includes at least one burner and at least one acoustic damper. The at least one burner includes a front panel having a front side and an opposing back side. The at least one acoustic damper is positioned on the back side of the front panel and includes at least one wall, at least one cooling air inlet, at least one outlet, and at least one cap. The at least one wall extends from the back side of the front panel and defines a dampening chamber. The at least one cooling air inlet is defined within the back side of the front panel and is configured to channel a flow of cooling air into the dampening chamber. The at least one outlet is defined within the back side of the front panel and is configured to channel the flow of cooling air out of the dampening chamber. The at least one cap positioned at least partially over the at least one cooling air inlet and configured to reduce a velocity of the flow of cooling air within the dampening chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary rotary machine;

FIG. 2 is a perspective view of an exemplary burner positioned with a combustor section of the rotary machine shown in FIG. 1;

FIG. 3 is a rear view of an exemplary front panel that may be positioned within the burner shown in FIG. 2;

FIG. 4 is a perspective view of an exemplary acoustic damper that may be positioned on a back side of the front panel shown in FIG. 3;

FIG. 5 is a perspective of an exemplary cap used with the acoustic damper shown in FIG. 4;

FIG. 6 is a cutaway top view of the cap shown in FIG. 4;

FIG. 7 is perspective view of an alternative cap that may be used with the acoustic damper shown in FIG. 4;

FIG. 8 is perspective view of another alternative cap that may be used with the acoustic damper shown in FIG. 4; and

FIG. 9 is a flow diagram of an exemplary method of manufacturing an acoustic damper, such as the acoustic damper shown in FIG. 4.

DETAILED DESCRIPTION

The exemplary acoustic dampers and methods described herein facilitate reducing a velocity of a cooling stream within the acoustic dampers, reducing acoustic oscillations within a burner, and reducing the ingestion of hot gas into the acoustic damper. The exemplary acoustic dampers described herein include at least one wall extending from a back side of a front panel of a burner. The wall and the back side of the front panel define a dampening chamber. The back side of the front panel also defines at least one cooling air inlet and at least one outlet. The cooling air inlet is oriented to channel a flow of cooling air into the dampening chamber, and the outlet is oriented to channel the flow of cooling air from the dampening chamber. The damper further includes at least one cap within a flow path of the cooling air and that extends from the back side of the front panel and over the cooling air inlet.

During operation, the outlet of the acoustic damper enables passage of acoustic oscillations into the acoustic damper, thus dampening the acoustic pressure oscillations, and reducing damage to the burner. The flow of cooling air into the dampening chamber cools the acoustic damper and facilitates reducing damage to the acoustic damper. A velocity of the flow of cooling air within the dampening chamber reduces a pressure within the dampening chamber. The reduced pressure may enable hot combustion gases to be ingested or channeled into dampening chamber, potentially causing damage to the acoustic damage. The cap facilitates reducing the velocity of the flow of cooling air and reducing potential damage to the acoustic damper caused by ingestion of combustion gases.

Unless otherwise indicated, approximating language, such as “generally,” “substantially,” and “about,” as used herein indicates that the term so modified may apply to only an approximate degree, as would be recognized by one of ordinary skill in the art, rather than to an absolute or perfect degree. Approximating language may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be identified. Such ranges may be combined and/or interchanged, and include all the sub-ranges contained therein unless context or language indicates otherwise.

Additionally, unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, for example, a “second” item does not require or preclude the existence of, for example, a “first” or lower-numbered item or a “third” or higher-numbered item.

FIG. 1 is a schematic view of an exemplary rotary machine 10 with which embodiments of the current disclosure may be used. In the exemplary embodiment, rotary machine 10 is a gas turbine that includes an intake section 12, a compressor section 14 coupled downstream from intake section 12, a combustor section 16 coupled downstream from compressor section 14, a turbine section 18 coupled downstream from combustor section 16, and an exhaust section 20 coupled downstream from turbine section 18. A generally tubular casing 36 at least partially encloses one or more of intake section 12, compressor section 14, combustor section 16, turbine section 18, and exhaust section 20. In alternative embodiments, rotary machine 10 is any machine having rotor blades for which the embodiments of the current disclosure are enabled to function as described herein. In the exemplary embodiment, turbine section 18 is coupled to compressor section 14 via a rotor shaft 22. It should be noted that, as used herein, the term “couple” is not limited to a direct mechanical, electrical, and/or communication connection between components, but may also include an indirect mechanical, electrical, and/or communication connection between multiple components.

During operation of gas turbine 10, intake section 12 channels air towards compressor section 14. Compressor section 14 compresses the air to a higher pressure and temperature. More specifically, rotor shaft 22 imparts rotational energy to at least one circumferential row of compressor blades 40 coupled to rotor shaft 22 within compressor section 14. In the exemplary embodiment, each row of compressor blades 40 is preceded by a circumferential row of compressor stator vanes 42 extending radially inward from casing 36 that direct the air flow into compressor blades 40. The rotational energy of compressor blades 40 increases a pressure and temperature of the air. Compressor section 14 discharges the compressed air towards combustor section 16.

In combustor section 16, compressed air is mixed with fuel and ignited to generate combustion gases that are channeled towards turbine section 18. More specifically, combustor section 16 includes at least one burner 24, in which a fuel, for example, natural gas and/or fuel oil, is injected into the air flow, and the fuel-air mixture is ignited to generate high temperature combustion gases that are channeled towards turbine section 18.

Turbine section 18 converts thermal energy from the combustion gas stream to mechanical rotational energy. More specifically, the combustion gases impart rotational energy to at least one circumferential row of rotor blades 70 coupled to rotor shaft 22 within turbine section 18. In the exemplary embodiment, each row of rotor blades 70 is preceded by a circumferential row of turbine stator vanes 72 extending radially inward from casing 36 that direct the combustion gases into rotor blades 70. Rotor shaft 22 may be coupled to a load (not shown) such as, but not limited to, an electrical generator and/or a mechanical drive application. The exhausted combustion gases flow downstream from turbine section 18 into exhaust section 20.

FIG. 2 is a perspective view of burner 24 positioned with combustor section 16 and including an exemplary front panel 90. FIG. 3 is a rear view of front panel 90 positioned within burner 24. Burner 24 includes at least one burner wall 80 that defines a burner chamber 82, a burner inlet 84, and a burner outlet 86. Front panel 90 is coupled to burner inlet 84 and defines a front panel inlet 92. Front panel 90 has a front side 94 and a back side 96 that is opposite front side 94. Front panel 90 is positioned on burner 24 such that back side 96 is coupled to burner 24, and front side 94 is oriented away from burner 24. As shown in FIG. 3, a plurality of acoustic dampers 100 extend across on back side 96 of front panel 90. In the exemplary embodiment, about thirty to about forty acoustic dampers 100 are positioned on back side 96 of front panel 90. However, any number of acoustic dampers 100 that enable burner 24 to operate as described herein may be positioned on back side 96 of front panel 90. Front panel 90 defines a plurality of outlets 102 that extend through front panel 90 from front side 94 to back side 96.

During operations, the flow of compressed air from compressor section 14 is channeled into burner 24 through front panel inlet 92 and burner inlet 84. A flow of fuel is injected into the flow of compressed air and the mixture of compressed air and fuel is ignited. Combustion within burner 24 may be unstable because the combustion dynamics within burner 24 may be unstable. Specifically, heat released during combustion, combined with the increased pressure caused by combustion, may cause acoustic pressure oscillations within burner 24. Acoustic pressure oscillations generally occur during normal operating conditions and may depend on a fuel-to-air stoichiometry within burner 24, a total mass flow within burner 24, and/or other operating conditions. The acoustic pressure oscillations may cause equipment damage or other operational problems. However, acoustic dampers 100 facilitate absorbing the acoustic pressure oscillations and/or reducing the amplitude of the pressure oscillations. Specifically, outlets 102 enable the acoustic pressure oscillations to enter acoustic dampers 100 where the acoustic pressure oscillations are dampened.

FIG. 4 is a perspective view of acoustic damper 100. Acoustic damper 100 includes at least one wall 104 that cooperates with back side 96 of front panel 90 to define a dampening chamber 106. In the exemplary embodiment, acoustic damper 100 also includes a top 108. Wall 104, top 108, and back side 96 of front panel 90 cooperate to define dampening chamber 106. Wall 104, top 108, and back side 90 are shown as transparent in FIG. 4.

In the illustrated embodiment, wall 104 in generally elliptical and extends substantially perpendicularly from back side 96. Specifically, in the illustrated embodiment, wall 104 includes two semicircular arcs 110 and two straight portions 112 that extend substantially perpendicularly from back side 96. Straight portions 112 extend continuously from semicircular arcs 110. Top 108 includes two half cones 114 on semicircular arcs 110 and two angled portions 116 on straight portions 112. Angled portions 116 are coupled to half cones 114 such that angled portions 116 form an elongated apex 118 defined between half cones 114. In the illustrated embodiment, semicircular arcs 110, straight portions 112, half cones 114, angled portions 116, elongated apex 118, and back side 96 of front panel 90 cooperate to define dampening chamber 106. Alternatively, acoustic damper 100 and dampening chamber 106 may have any other shape that enables acoustic damper 100 to function as described herein. Specifically, the shape of acoustic damper 100 and dampening chamber 106 may be determined by computation fluid dynamic (CFD) analysis and may be selected based on the fuel-to-air stoichiometry within burner 24, the total mass flow within burner 24, and/or any other operating condition.

As shown in FIG. 4, at least one outlet 102 extends through front panel 90 from front side 94 to back side 96. Outlet 102 enables the acoustic pressure oscillations to enter dampening chamber 106 wherein the acoustic pressure oscillations are dampened. In the exemplary embodiment, outlet 102 is a circular conduit extending through front panel 90. Alternatively, outlet 102 may have any other shape that that enables acoustic damper 100 to function as described herein. Specifically, the shape of outlet 102 a may be determined by CFD analysis and may be selected based on the fuel-to-air stoichiometry within burner 24, the total mass flow within burner 24, and/or any other operating condition. Additionally, although the exemplary embodiment only includes a single outlet 102 for each acoustic damper 100, acoustic damper 100 may include any number of outlets 102 that enables acoustic damper 100 to operate as described herein, including, without limitation, two, three, or more outlets 102. Specifically, the number of outlets 102 included with each acoustic damper 100 may be determined by CFD analysis and may be selected based on the fuel-to-air stoichiometry within burner 24, the total mass flow within burner 24, and/or any other operating condition.

Back side 96 of front panel 90 defines at least one cooling air inlet 120 and/or 122. Specifically, in the exemplary embodiment, back side 96 of front panel 90 defines a first cooling air inlet 120 and a second cooling air inlet 122. cooling air inlets 120 and 122 are oriented to channel a flow of cooling air, as indicated by arrows 124 and 126, into dampening chamber 106. Specifically, first cooling air inlet 120 is oriented to channel a first flow of cooling air, as indicated by arrow 124, and second cooling air inlet 122 is oriented to channel a second flow of cooling air, as indicated by arrow 126. However, acoustic damper 100 may include any other number of cooling air inlets 120 and 122 that enables acoustic damper 100 to function as described herein, including, without limitation, one, three, or more cooling air inlets 120 and 122. Specifically, the number of cooling air inlets 120 and 122 included with each acoustic damper 100 may be determined by CFD analysis and may be selected based on the fuel-to-air stoichiometry within burner 24, the total mass flow within burner 24, and/or any other operating condition. In the exemplary embodiment, the source of flow of cooling air 124 and 126 is compressor section 14, and flow of cooling air 124 and 126 typically has a higher pressure than the combustion gases, such that flow of cooling air 124 and 126 is channeled out of acoustic damper 100 through outlet 102. As such, cooling air inlets 120 and 122 are oriented to channel flow of cooling air 124 and 126 into dampening chamber 106, and outlet 102 is oriented to channel flow of cooling air 124 and 126 from dampening chamber 106.

During operations, burner 24 ignites the fuel-air mixture and generates high temperature combustion gases that are channeled towards turbine section 18. Heat released during combustion combined with the increased pressure caused by combustion may cause acoustic pressure oscillations to develop within burner 24. The acoustic pressure oscillations enter acoustic damper 100 through outlet 102 and are dampened within dampening chamber 106. Heat released during combustion may damage acoustic damper 100, and cooling air inlets 120 and 122 channel cooling air 124 and 126 into acoustic damper 100 to reduce a temperature of acoustic damper 100 and to facilitate reducing damage caused by the heat released during combustion. However, a high velocity of flow of cooling air 124 and 126 within dampening chamber 106 may reduce a pressure within dampening chamber 106, thus enabling hot combustion gases to be drawn into the dampening chamber 106. The hot gases may cause damage to acoustic damper 100.

To reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106, at least one cap 128 and/or 130 is positioned within dampening chamber 106 partially over cooling air inlets 120 and 122. In the illustrated embodiment, a plurality of caps 128 and 130 are positioned within dampening chamber 106 such that caps 128 and 130 extend at least partially across cooling air inlets 120 and 122. Specifically, a first cap 128 partially covers first cooling air inlet 120, and a second cap 130 partially covers second cooling air inlet 122. Each cap 128 and 130 is positioned within the path of flow of cooling air 124 and 126 to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and to reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106. As such, caps 128 and 130 facilitate reducing the ingestion of combustion gasses into dampening chamber 106 and reduce damage to acoustic damper 100 caused by the ingestion of combustion gases.

FIG. 5 is a perspective view of first cap 128 within acoustic damper 100. Wall 104, top 108, and back side 90 are shown as transparent in FIG. 5. FIG. 6 is a cutaway top view of first cap 128. In the illustrated embodiment, caps 128 and 130 are hollow, semispherical coverings or cups that extend from back side 96 and substantially cover cooling air inlets 120 and 122. Specifically, each cap 128 and 130 has a semispherical shell 132 that defines a cap opening 134. Shell 132 is positioned within the path of flow of cooling air 124 and 126 to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and to facilitate reducing the velocity of flow of cooling air 124 and 126 within dampening chamber 106. Specifically, shell 132 is positioned over cooling air inlets 120 and 122 such that cap opening 134 faces away from outlet 102.

Cap opening 134 is oriented to channel flow of cooling air 124 and 126 into dampening chamber 106. Additionally, cooling air inlets 120 and 122 are oriented to channel flow of cooling air 124 and 126 into a back of shell 132 such that flow of cooling air 124 and 126 has to turn in order to exit cap opening 134. Moreover, because cap opening 134 is oriented away from outlet 102, cooling air 124 and 126 has to turn again in order to exit acoustic damper 100 through outlet 102. As such, caps 128 and 130 are positioned over cooling air inlets 120 and 122 to force flow of cooling air 124 and 126 to follow a tortuous path within dampening chamber 106. Accordingly, caps 128 and 130 disrupt flow of cooling air 124 and 126 within dampening chamber 106 and reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106. As such, caps 128 and 130 facilitate reducing the ingestion of combustion gasses into dampening chamber 106 and facilitate reducing damage to acoustic damper 100 caused by the ingestion of combustion gases.

In the illustrated embodiment, shell 132 has a semi-spherical shape. However, shell 132 may have any other shape that enables acoustic damper 100 to function as described herein including, without limitation, cylindrical and/or parallelepipedal shapes. Specifically, the shape of each shell 132 may be determined by CFD analysis and may be changed based on the fuel-to-air stoichiometry within burner 24, the total mass flow within burner 24, and/or any other operating condition. Additionally, caps 128 and 130 may each have the same shape or caps 128 and 130 may each have a different shape.

As shown in FIG. 6, each cap 128 and 130 has a cap diameter 136 and a cut distance 138 that extends substantially perpendicularly from cap diameter 136 to cap opening 134. Cut distance 138 determines the size of cap opening 134. Increasing cut distance 138 moves cap opening 134 away from a center 140 of cap 128 and 130 and reduces the size of cap opening 134. Conversely, decreasing cut distance 138 moves cap opening 134 toward center 140 of cap 128 and 130 and increases the size of cap opening 134. In the exemplary embodiment, cap diameter 136 is about 4 millimeters (mm) to about 10 mm. More specifically, in the exemplary embodiment, cap diameter 136 is about 6 mm. In the exemplary embodiment, cut distance 138 is between about 0.5 mm to about 5 mm. More specifically, in the exemplary embodiment, cut distance 138 is about 1.2 mm.

Cap diameter 136 and cut distance 138 are determined by CFD analysis such that caps 128 and 130 disrupt flow of cooling air 124 and 126 within dampening chamber 106 and reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106. However, caps 128 and 130 may have any cap diameter 136 and/or cut distance 138 that enables acoustic damper 100 to operate as described herein. Additionally, caps 128 and 130 may each have the same cap diameter 136 and/or cut distance 138, or caps 128 and 130 may each have different cap diameter 136 and cut distance 138.

In the exemplary embodiment, acoustic damper 100 includes two caps 128 and 130, one for each cooling air inlets 120 and 122. However, acoustic damper 100 may include any number of caps 128 and 130 that enables acoustic damper 100 to operate as described herein, including, without limitation, one, three, or more caps 128 and 130. Specifically, first cap 128 may be positioned over first cooling air inlet 120, but second cooling air inlet 122 may not be covered by second cap 130. The number of caps 128 and 130 may be determined by a CFD analysis which determines the number of caps 128 and 130 required to facilitate reducing ingestion of hot combustion gases into acoustic damper 100. Additionally, each cap 128 and 130 has a position within acoustic damper 100 relative to wall 104. Specifically, each cap 128 and 130 is positioned a cap distance 142 from wall 104. Cap distance 142 is a distance from a center 144 of cap opening 134 to wall 104. Cap distance 142 determines an amount of space between cap 128 and 130 and wall 104 and determines the amount of space flow of cooling air 124 and 126 has to turn toward outlet 102.

Increasing cap distance 142 increases the amount of space that cooling air 124 and 126 has to turn towards outlet 102 and decreases resistance to flow of cooling air 124 and 126 which increases a velocity of flow of cooling air 124 and 126. Conversely, decreasing cap distance 142 decreases an amount of space that cooling air 124 and 126 has to turn towards outlet 102 and increases the resistance to flow of cooling air 124 and 126 which decreases the velocity of flow of cooling air 124 and 126. In the exemplary embodiment, cap distance 142 is about 0.5 mm to about 10 mm. More specifically, in the exemplary embodiment, cap distance 142 is about 1 mm. A CFD analysis determines the position of each cap 128 and 130 by adjusting cap distance 142 to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106. Additionally, the CFD analysis also simultaneously adjusts cap diameter 136 and cut distance 138 for each cap 128 and 130 to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106. Moreover, in alternative embodiments, shell 132 may be positioned over cooling air inlets 120 and 122 such that cap opening 134 is positioned in any orientation relative to outlet 102 that enables caps 128 and 130 to operate as described herein.

Cap diameter 136, cut distance 138, and cap distance 142 are adjusted for each cap 128 and 130 to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and to reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106 in order to reduce ingestion of hot combustion gases into dampening chamber 106 and to reduce damage to acoustic damper 100. Specifically, a CFD analysis adjusts cap diameter 136, cut distance 138, and cap distance 142 such that ingestion of hot combustion gases is reduced. Accordingly, caps 128 and 130 facilitate reducing ingestion of hot combustion gases into acoustic damper 100, reduce damage to acoustic damper 100, and improve the reliability of burner 24 and rotary machine 10.

FIG. 7 is perspective view of a cap 700. FIG. 8 is perspective view of a cap 800. Caps 700 and 800 are alternative embodiments of caps 128 and 130. Cap opening 134 of cap 700 includes a plurality of cap holes 702 rather than cap opening 134 described above and cap opening 134 of cap 800 includes a plurality of cap holes 802 rather than cap opening 134 described above. Cap holes 702 are configured to channel flow of cooling air 124 and 126 out of shell 132 and into dampening chamber 106. In the illustrated embodiment, cap holes 702 are circular holes extending through shell 132. However, cap holes 702 may have any shape that enables cap 700 to operate as described herein. In the illustrated embodiment, cap 700 includes three cap holes 702 arranged linearly. However, cap 700 may include any number of cap holes 702 in any arrangement that enables cap 700 to operate as described herein. Cap holes 702 reduce the area that flow of cooling air 124 and 126 has to flow out of shell 132 as compared to cap opening 134 and increases resistance to flow of cooling air 124 and 126 which decreases the velocity of flow of cooling air 124 and 126. Accordingly, cap 700 further decreases the velocity of flow of cooling air 124 and 126 as compared to caps 128 and 130.

Cap 800 is similar to cap 700 except that cap 800 includes more cap holes 802 arranged linearly in two rows. Cap holes 802 are also larger than cap holes 702. As such, cap holes 802 reduce the area that flow of cooling air 124 and 126 has to flow out of shell 132 as compared to cap opening 134, but cap holes 802 increase the area that flow of cooling air 124 and 126 has to flow out of shell 132 as compared to cap holes 702. Accordingly, cap 800 decreases the velocity of flow of cooling air 124 and 126 as compared to caps 128 and 130 and increases the velocity of flow of cooling air 124 and 126 as compared to cap 700. The velocity of flow of cooling air 124 and 126 may be tuned by adjusting cap opening 134 of caps 128 and 130, 700, and 800. Specifically, cap opening 134 of first cap 128 may include cap holes 702 while cap opening 134 of second cap 130 may include cap opening 134 described above. As such, cap opening 134 of caps 128 and 130, 700, and 800 may be adjusted to disrupt flow of cooling air 124 and 126 within dampening chamber 106 and reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106 in order to reduce ingestion of hot combustion gases into dampening chamber 106 and reduce damage to acoustic damper 100.

FIG. 9 is a flow diagram of an exemplary method 900 of manufacturing acoustic damper 100. The method 900 includes defining 902 at least one outlet 102 to extend through front panel 90. Outlets 102 extend from front side 94 of front panel 90 to back side 96 of front panel 90. Method 900 also includes defining 904 at least one cooling air inlets 120 and 122 within back side 96 of front panel 90. Method 900 further includes forming 906 at least one wall 104 on back side 96 of front panel 90. Wall 104 and back side 96 of front panel 90 define dampening chamber 106. Method 900 also includes forming 908 at least one cap 128 on back side 96 of front panel 90. Cap 128 is oriented to reduce the velocity of flow of cooling air 124 and 126 within dampening chamber 106.

Acoustic dampers 100 described herein may be manufactured using any manufacturing technique that enables acoustic damper 100 to operate as described herein. In the exemplary embodiment, each acoustic damper 100 is manufactured by additively manufacturing acoustic damper 100 and front panel 90. Specifically, front panel 90 is additively manufactured to define outlets 102 and cooling air inlets 120 and 122 within front panel 90. Acoustic dampers 100 and caps 128 are then additively manufactured on back side 96 of front panel 90. Additively manufacturing reduces the cost and time to form caps 128 within acoustic dampers 100. As such, additively manufacturing acoustic damper 100 facilitates reducing the cost and manufacturing time to produce acoustic dampers 100 with caps 128 while increasing the reliability of burner 24 and rotary machine 10.

The exemplary acoustic dampers and methods described herein facilitate reducing a velocity of a cooling stream within the acoustic dampers, reducing acoustic oscillations within a burner, and reducing the ingestion of hot gas into the acoustic damper. The exemplary acoustic dampers described herein include at least one wall extending from a back side of a front panel of a burner. The wall and the back side of the front panel define a dampening chamber. The back side of the front panel also defines at least one cooling air inlet and at least one outlet. The cooling air inlet is oriented to channel a flow of cooling air into the dampening chamber, and the outlet is oriented to channel the flow of cooling air from the dampening chamber. The damper further includes at least one cap within a flow path of the cooling air and that extends from the back side of the front panel and over the cooling air inlet.

During operation, the outlet of the acoustic damper enables passage of acoustic oscillations into the acoustic damper, thus dampening the acoustic pressure oscillations, and reducing damage to the burner. The flow of cooling air into the dampening chamber cools the acoustic damper and facilitates reducing damage to the acoustic damper. A velocity of the flow of cooling air within the dampening chamber reduces a pressure within the dampening chamber. The reduced pressure may enable hot combustion gases to be ingested or channeled into dampening chamber, potentially causing damage to the acoustic damage. The cap facilitates reducing the velocity of the flow of cooling air and reducing potential damage to the acoustic damper caused by ingestion of combustion gases.

The methods, apparatus, and systems described herein are not limited to the specific embodiments described herein. For example, components of each apparatus or system and/or steps of each method may be used and/or practiced independently and separately from other components and/or steps described herein. In addition, each component and/or step may also be used and/or practiced with other assemblies and methods.

While the disclosure has been described in terms of various specific embodiments, those skilled in the art will recognize that the disclosure can be practiced with modification within the spirit and scope of the claims. Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. Moreover, references to “one embodiment” in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 

What is claimed is:
 1. An acoustic damper for a rotary machine, said acoustic damper comprising: at least one wall extending from a back side of a combustion chamber front panel, such that said at least one wall at least partially defined a dampening chamber; at least one cooling air inlet defined within the back side of the front panel, said at least one cooling air inlet oriented to channel a flow of cooling air into the dampening chamber; at least one outlet defined within the back side of the front panel, said at least one outlet oriented to channel the flow of cooling air out of the dampening chamber; and at least one cap extending at least partially over said at least one cooling air inlet and oriented to reduce a velocity of the flow of cooling air within the dampening chamber.
 2. The acoustic damper of claim 1, wherein said at least one cooling air inlet comprises a first cooling air inlet and a second cooling air inlet.
 3. The acoustic damper of claim 2, wherein said at least one cap comprises a first cap positioned partially over said first cooling air inlet and a second cap positioned partially over said second cooling air inlet.
 4. The acoustic damper of claim 1, wherein said at least one cap defines a cap opening configured to channel the flow of cooling air into said dampening chamber.
 5. The acoustic damper of claim 4, wherein said at least one cap is positioned over said at least cooling air inlet such that said cap opening faces away from said at least one outlet.
 6. The acoustic damper of claim 1, wherein said at least one cap comprises at least one semi-spherical shell.
 7. The acoustic damper of claim 6, wherein at least one semispherical shell defines a cap diameter of about 4 millimeters to about 10 millimeters.
 8. The acoustic damper of claim 1, wherein said at least one cap defines at least one cap hole configured to channel the flow of cooling air into said dampening chamber.
 9. The acoustic damper of claim 8, wherein said at least one cap hole comprises a plurality of cap holes.
 10. A method of manufacturing an acoustic damper for use in a burner, said method comprising: defining an outlet through a front panel of the burner, wherein the outlet extends from a front side of the front panel to a back side of the front panel; defining at least one cooling air inlet within the back side of the front panel; forming at least one wall on the back side of the front panel, wherein the at least one wall and the back side of the front panel define a dampening chamber; and forming at least one cap positioned at least partially over the at least one cooling air inlet, the at least one cap configured to facilitate reducing a velocity of a flow of cooling air within the dampening chamber.
 11. The method of claim 10, wherein defining at least one cooling air inlet within the back side of the front panel comprises defining a first cooling air inlet and a second cooling air inlet within the back side of the front panel.
 12. The method of claim 11, wherein forming at least one cap positioned at least partially over the at least one cooling air inlet comprises forming a first cap positioned at least partially over the first cooling air inlet and a second cap positioned at least partially over the second cooling air inlet.
 13. The method of claim 10, further comprising forming at least one cap opening within the at least one cap.
 14. The method of claim 10, further comprising forming at least one cap hole within the at least one cap.
 15. A rotary machine comprising: at least one burner comprising a front panel having a front side and an opposing back side; and at least one acoustic damper positioned on said back side of said front panel, said at least one acoustic damper comprising: at least one wall extending from said back side of said front panel, such that said at least one wall partially defines a dampening chamber; at least one cooling air inlet defined within said back side of said front panel, said at least one cooling air inlet oriented to channel a flow of cooling air into said dampening chamber; at least one outlet defined within said back side of said front panel, said at least one outlet oriented to channel the flow of cooling air out of said dampening chamber; and at least one cap extending at least partially over said at least one cooling air inlet and oriented to reduce a velocity of the flow of cooling air within the dampening chamber.
 16. The rotary machine of claim 15, wherein said at least one cooling air inlet comprises a first cooling air inlet and a second cooling air inlet.
 17. The rotary machine of claim 16, wherein said at least one cap comprises a first cap positioned partially over said first cooling air inlet and a second cap positioned partially over said second cooling air inlet.
 18. The rotary machine of claim 15, wherein said at least one cap defines a cap opening configured to channel the flow of cooling air into said dampening chamber.
 19. The rotary machine of claim 18, wherein said at least one cap is positioned over said at least cooling air inlet such that said cap opening faces away from said at least one outlet.
 20. The rotary machine of claim 15, wherein said at least one cap comprises at least one semispherical shell. 